

if __name__ == "__main__":
    score = input("请输入分数：")
    while score != "e":
        score = int(score)
        if score < 60:
            print("D")
        elif score < 80:
            print("C")
        elif score < 90:
            print("B")
        elif score < 100:
            print("A")
        elif score == 100:
            print("S")
        score = input("请输入分数：")
